Farmall H 12 V Coil

I suspect my coil is bad. Is there a way to measure the resistance of this coil to tell if its bad? What is this part number so I can buy a new one. My Farmall H ran several years ago with this coil. I have a 1949 Farmall H with a 12 volts system and a delco distributor.
 
If there is no ballast resistor, you will need a 12v coil with no resistor required. It should have about 4 ohms from little
terminal to little terminal with one of them disconnected. The resistance from either of the small terminals to the center tower
should be in the 7 to 10 thousand ohm range. If no connection from terminal to terminal, it is for sure bad. Even if the Ohms
read OK, it can still be bad from a high voltage path to ground that can't be tested as above. IC14SB is a NAPA number. If it
has a resistor (ceramic block at the coil area), it needs a resistor required coil, or a 6v coil 12v 903 will work. Jim
 
I tried to attach a picture of the coil. I don't have a ballast resistor. I will try those measurements, thanks.
mvphoto25244.jpg
 
The coil you show needs a ballast resistor (1966 chevy 6 cylinder bel air would work well. The way it is, it probably got too hot, or ruined the points because it is
running on far more volts than it should. It is basically a 6v coil. If it is toast, use a 12v no resistor required as indicated in my other post. If it is good, use a
resistor. Jim
 
FWIW I agree with Jim. The coil shown is more like a 6 volt coil and just as it says on a 12 volt tractor if you don't have an external series in line voltage dropping (12 to 6) ballast resistor it runs hot will eventually fail plus the points will burn prematurely. While an ohm meter can show if a coil is totally bad ((an open circuit) it does NOT prove its good because often its HV breakdown only after warmed up it fails. If the coil shows good to an ohm meter and is actually fully okay you still need to EITHER use a full true 12 volt rated coil (NO ballast required) or else that or another 6 volt coil PLUS an external series voltage dropping (12 to 6) ballast resistor.

John T
 
(quoted from post at 03:42:02 10/15/18) FWIW I agree with Jim. The coil shown is more like a 6 volt coil and just as it says on a 12 volt tractor if you don't have an external series in line voltage dropping (12 to 6) ballast resistor it runs hot will eventually fail plus the points will burn prematurely. While an ohm meter can show if a coil is totally bad ((an open circuit) it does NOT prove its good because often its HV breakdown only after warmed up it fails. If the coil shows good to an ohm meter and is actually fully okay you still need to EITHER use a full true 12 volt rated coil (NO ballast required) or else that or another 6 volt coil PLUS an external series voltage dropping (12 to 6) ballast resistor.

John T

Tractors Guru(s),
Thanks for letting me know about my 12 v coil issue. I ordered the NAPA coil as you suggested, so I will be using the correct coil. Sounds like I need to investigate the points and probably safe to replace those too.
 

I put the new (correct) Coil on that I got from NAPA today. Both the new and old Coil measured good on their resistance. I bought a spark tool to fit inline with plug wires. I measured 12 VDC at the Coil and distributor with Ignition Switch ON. The spark across all 4 plug wires and main Coil wire did not light. So it must be a points problem? I have not changed points? Do I need to remove distributor? If I need too, is there anything I need to be careful of when removing it? Is it easy to put back in? What part number for a new set of points that I need to look for? Or is there something else I should do, before changing points? Sorry for all these questions as I am use to electronic ignitions and not use to points. Sorry for my lack of experience.
mvphoto25317.jpg


mvphoto25318.jpg
 
The points look corroded (or burnt). Look at the name plate on the distributor, it probably says Autolite or Delco. take the number from the plate to get points. It is
not an IHC distributor. Jim
 
"I measured 12 VDC at the Coil and distributor with Ignition Switch ON." The wire from small terminal on coil to distributor should read near battery voltage with points open and near zero with points closed. Do you get zero with points closed? If not you might get by cleaning the points contacts.

Is that a cut or pinched spot on the condenser wire? Is it cut on bottom of wire and touching on edge of distributor?

" I have not changed points? Do I need to remove distributor?" Absolutely not.

When you get new points installed, take a piece of the box flap the points came in and draw it through the closed points to clean them
 
(quoted from post at 18:52:11 10/15/18) "I measured 12 VDC at the Coil and distributor with Ignition Switch ON." The wire from small terminal on coil to distributor should read near battery voltage with points open and near zero with points closed. Do you get zero with points closed? If not you might get by cleaning the points contacts.

Is that a cut or pinched spot on the condenser wire? Is it cut on bottom of wire and touching on edge of distributor?

" I have not changed points? Do I need to remove distributor?" Absolutely not.

When you get new points installed, take a piece of the box flap the points came in and draw it through the closed points to clean them

I measured 12v with points open and closed, so looks like points are bad. I ordered new points for $5. Thanks for the help. The points are probably bad because I was using the wrong Coil and burnt out the points. I will follow this up, when I get new points installed.
 
If all is well and wired correct, if you put a test lamp or voltmeter on the coils INPUT (from ign switch) and ignition is ON, the lamp should light and you should get battery voltage. HOWEVER if you put the test lamp over on the coils OUTPUT (to distributor) the lamp should glow (battery voltage) when points are OPEN but go off (near 0 volts) when points are CLOSED.

John T
 
If all is well and wired correct, if you put a test lamp or voltmeter on the coils INPUT (from ign switch) and ignition is ON, the lamp should light and you should get battery voltage. HOWEVER if you put the test lamp over on the coils OUTPUT (to distributor) the lamp should glow (battery voltage) when points are OPEN but go off (near 0 volts) when points are CLOSED.

Shouldn't have to remove the distributor just to change points

John T
 
Do yourself a big favor and forget the $5 points. Go to an auto parts store and get a set of Echlin, Standard Blue Streak or equivalent.
 
(quoted from post at 18:09:19 10/15/18)
I put the new (correct) Coil on that I got from NAPA today. Both the new and old Coil measured good on their resistance. I bought a spark tool to fit inline with plug wires. I measured 12 VDC at the Coil and distributor with Ignition Switch ON. The spark across all 4 plug wires and main Coil wire did not light. So it must be a points problem? I have not changed points? Do I need to remove distributor? If I need too, is there anything I need to be careful of when removing it? Is it easy to put back in? What part number for a new set of points that I need to look for? Or is there something else I should do, before changing points? Sorry for all these questions as I am use to electronic ignitions and not use to points. Sorry for my lack of experience.

You have a common Delco Remy distributor.

Points are the same as 50's-ish vehicles used.

GM/AC Delco changed the numbers over the years, #1855720, #1857957, #1911119, #1924571, #D100, #D100H, #D100HP, #D100P, #D105, #D105P, #D111, ANY autoparts store should be able to cross over to the brand they sell
 
Thanks John, I measured 12 volts with points open and closed. I am getting new points and see some people say to set the gap at 0.14 inches and others say 0.20 inches. What is the correct gap distance?
 
(quoted from post at 04:19:49 10/16/18) If all is well and wired correct, if you put a test lamp or voltmeter on the coils INPUT (from ign switch) and ignition is ON, the lamp should light and you should get battery voltage. HOWEVER if you put the test lamp over on the coils OUTPUT (to distributor) the lamp should glow (battery voltage) when points are OPEN but go off (near 0 volts) when points are CLOSED.

Shouldn't have to remove the distributor just to change points

John T

I put the new points in and now I have a spark. I set the gap at 0.020 inches. When I tried to start my Farmall H, it would try to start but could not get it to Idle. I know my gas level is low, so next time I will put gas in and hope it runs. I had the carb rebuilt so that might need some adjustment too? I set both carb adjustment screws to 2 turns as a starting point.
 

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